Materials, systems, and methods for co2 capture and conversion

ABSTRACT

A method of capturing CO2 and converting the captured CO2 into useful byproducts includes providing a material including a material matrix holding an ionic liquid, exposing the material to a source of thermal energy to capture CO2 within the material, removing the material from exposure to the source of thermal energy, and washing the material with a solution to convert the captured CO2 and wash the converted, captured CO2 from the material as filtrate. Materials and systems for capturing CO2 and converting the captured CO2 into useful byproducts are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/624,333, filed on Jan. 31, 2018, the entirecontents of which is hereby incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to CO₂ reduction and, more specifically,to materials, systems, and methods for CO₂ capture and conversion intouseful byproducts.

Background of Related Art

Since the industrial revolution, CO₂ emissions have increaseddramatically due largely to the transportation, building, and industrialsectors and the corresponding exponential increase in the usage offossil fuels. In fact, CO₂ emissions have increased at the alarming rateof approximately 40% globally over the last 10 to 15 years, and thisnumber is expected to double by 2050.

Due to the massive increase in CO₂ emissions, one of the major areas ofemphasis on the global energy market is the reduction of greenhousegases, specifically CO₂. The capture of CO₂ is viewed as one of the mostprominent means of decarburization. Several studies have been publishedthat describe the importance of CO₂ capture and strategies to cutemissions by half in the US. With an increasing demand for this domainof research, a variety of mechanisms are being explored for effectiveCO₂ capture.

Currently, commercial systems and methods employed for CO₂ captureinclude amine-based solvents, mainly monoethanolamine (MEA),diethanolamine, and methyldienthanolamine. However, the limited capacityfor the capture of CO₂, toxicity of the resultant chemicals, loss ofreagent due to evaporation, equipment corrosion, and large enthalpy ofreaction corresponding to higher energy requirements considerablyreduces the efficiency of these current systems and methods.

It would therefore be desirable to provide reusable materials, systems,and methods capable of effectively and efficiently capturing CO₂ andconverting the captured CO₂ into useful byproducts in a cyclic,repeatable manner.

SUMMARY

The present disclosure provides effective and efficient materials,systems, and methods for CO₂ capture and conversion into usefulbyproducts. More specifically, the present disclosure provides stable,sustainable, cyclically repeatable CO₂ collection materials, systems,and methods activated by solar heat localization. These materials,systems, and methods utilize ionic liquids and a graphene aerogel, whichundergoes solid-liquid phase change to efficiently capture CO₂ at a rateof 0.2 moles of CO₂ for every mole of ionic liquid and converts theabsorbed CO₂ into useful byproducts, e.g., water and calcium carbonate,in each cycle. These and other aspects and features of the presentdisclosure are detailed below. To the extent consistent, any of theaspects and features detailed herein may be used in conjunction with anyor all of the other aspects and features detailed herein.

Provided in accordance with aspects of the present disclosure is amethod of capturing CO₂ and converting the captured CO₂ into usefulbyproducts. The method includes providing a material including amaterial matrix holding an ionic liquid, exposing the material to asource of thermal energy (e.g., employing solar heat localization) tocapture CO₂ within the material, removing the material from exposure tothe source of thermal energy, and washing the material with a solutionto convert the captured CO₂ and wash the converted, captured CO₂ fromthe material as filtrate.

In aspects of the present disclosure, the method further includesseparating the filtrate into at least one useful byproduct. Separatingthe filtrate into at least one useful byproduct may be accomplished, inaspects, by allowing the filtrate to sit for a period of time ortreating the filtrate with additional solution.

In aspects of the present disclosure, the filtrate is separated intobyproducts including H₂O and/or CaCO₃.

In aspects of the present disclosure, the solution is an aqueous Ca(OH)₂solution.

In aspects of the present disclosure, the method further includescyclically repeating, a plurality of additional times: exposing thematerial to the source of thermal energy to capture CO₂ within thematerial, removing the material from exposure to the source of thermalenergy, and washing the material with the solution to convert thecaptured CO₂ and wash the converted, captured CO₂ from the material asfiltrate.

In aspects of the present disclosure, exposing the material to thesource of thermal energy includes exposing the material to solarillumination.

A material provided in accordance with the present disclosure andconfigured to capture CO₂ and able to be washed of the captured CO₂includes an ionic liquid, e.g., a commercially-available ionic liquid ora fluorinated ionic liquid, having a melting point of from 30° C. to 70°C., and a material matrix. The ionic liquid is configured to capture CO₂in response to exposure to a thermal energy source. The material matrixis permeable and porous, hydrophobic, and oleophilic and is configuredto hold the ionic liquid therein.

In aspects of the present disclosure, the material matrix is an aerogeland, more specifically, in aspects, a graphene aerogel.

In aspects of the present disclosure, the ionic liquid is thecommercially-available ionic liquid C10MI.BF₄ or C16MI.Tf₂N, or thefluorinated ionic liquid CF₃(CF₂)₇(CH₂)₃MI][(CF₃—CF₂SO₂)₂N.

In aspects of the present disclosure, the ionic liquid is washable towash out CO₂ captured therein.

A system provided in accordance with the present disclosure andconfigured to capture CO₂ and convert the captured CO₂ into usefulbyproducts includes a CO₂ absorber including an ionic liquid and amaterial matrix, and a washing solution. The ionic liquid has a meltingpoint of from 30° C. to 70° C. and is configured to capture CO₂ inresponse to exposure to a thermal, e.g., solar, energy source. Thematerial matrix is permeable and porous, hydrophobic, and oleophilic,and is configured to hold the ionic liquid therein. The washing solutionis configured to wash captured CO₂ from the CO₂ absorber and convert itinto useful byproducts.

In aspects of the present disclosure, the material matrix includes agraphene aerogel.

In aspects of the present disclosure, the ionic liquid is fluorinated.

In aspects of the present disclosure, the solution is an aqueous Ca(OH)₂solution.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and features of the present disclosure are describedhereinbelow with reference to the drawings wherein like numeralsdesignate similar elements in each of the several views and:

FIG. 1A is a schematic diagram illustrating a material provided inaccordance with the present disclosure for CO₂ capture and conversion;

FIG. 1B is a schematic diagram illustrating the material of FIG. 1Abeing exposed to solar energy and capturing CO₂;

FIG. 1C is a schematic diagram of the material of FIG. 1A after it hascaptured CO₂ via exposure to solar energy, illustrating the materialbeing washed to convert and remove the CO₂ from the material;

FIG. 1D is a schematic diagram illustrating the byproducts of the CO₂capture and conversion illustrated in FIGS. 1A-1C;

FIG. 2 is a flow diagram illustrating a method of CO₂ capture andconversion provided in accordance with the present disclosure;

FIGS. 3 and 4 are schematic illustrations of experimental setupsconfigured to measure the absorption of CO₂ utilizing the materials andmethods of the present disclosure;

FIG. 5A is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, with CM10MI.BF₄ as the ionicliquid, illustrating Fourier-Transform Infrared (FTIR) spectra for thecapture of CO₂;

FIG. 5B is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, with C16MI.Tf₂N and a fluorinatedionic liquid (FIL) as the ionic liquids, illustrating FTIR spectra forthe capture of CO₂;

FIG. 5C is a graph of results from a pressure drop experiment utilizingthe materials and methods of the present disclosure, illustrating CO₂capture in terms of mole fraction;

FIG. 5D is a graph of results from a pressure drop experiment utilizingthe materials and methods of the present disclosure, illustrating CO₂capture in terms of a change in percentage of CO₂;

FIG. 6A is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, illustrating FTIR spectra toverify CO₂ presence before and after washing with Ca(OH)₂;

FIG. 6B is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, illustrating aUltraviolet-visible (UV-vis) spectrum for the Ca(OH)₂ solution used forwashing and the filtrate formed after washing (verifying information ofCa(HCO₃)₂);

FIG. 6C is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, illustrating pH measurements toverify formation of Ca(HCO₃)₂ in the filtrate upon washing with Ca(OH)₂;

FIG. 6D is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, illustrating FTIR spectra for thefinal precipitated CaCO₃ and comparison with commercially availableCaCO₃;

FIG. 7 is a graph of results from an experiment utilizing the materialsand methods of the present disclosure, illustrating repeatability over aplurality of cycles; and

FIG. 8A is a side view of a test tube including precipitated CaCO₃ andwater byproducts of an experiment utilizing the materials and methods ofthe present disclosure, after a first cycle; and

FIG. 8B is a side view of a test tube including precipitated CaCO₃ andwater byproducts of the experiment of FIG. 8A, after a fifth cycle.

DETAILED DESCRIPTION

Referring to FIGS. 1A-1D and 2, provided in accordance with the presentdisclosure is a material, referred to herein as a Reusable CarbonDioxide (CO₂) Absorber (RCA), configured to capture CO₂ and convert thecaptured CO₂ into useful byproducts such as, for example, precipitatedcalcium carbonate (CaCO₃) and water (H₂O). CaCO₃ is useful for manypurposes including water treatment and the manufacture of paints,plastics, papers, sealants, adhesives, inks, cement, plaster, mortars,pharmaceuticals, and nutritional supplements, to name a few. For thepurposes herein, the term “useful byproduct” refers to any byproductthat is non-toxic and is itself utilized in a generally-accepted mannerin the industry or field for which it pertains and/or utilized in aprocess (e.g., a treatment process, a manufacturing process, etc.) thatis generally-accepted in the industry or field for which it pertains.Systems and methods for capturing CO₂ and converting the captured CO₂into useful byproducts are also provided in accordance with the presentdisclosure.

With initial reference to FIG. 1A and step S210 of FIG. 2, RCA 100,described in greater detailed below, includes a material matrix holdingan ionic liquid. RCA 100 may be incorporated into a suitable system (notexplicitly shown) to facilitate CO₂ capture under solar illumination, orvia another thermal energy source 110. Such a system may include, forexample, a chamber retaining RCA 100 therein, a cover covering thechamber and configured for efficient transmission of solar irradiationtherethrough, and an input and output defined into and out of thechamber, respectively. Any suitable system, including large-scalesystems, may be utilized and are within the scope of the presentdisclosure.

Referring also to FIG. 1B and step S220 of FIG. 2, when RCA 100 isexposed to a thermal energy source 110 such as, for example, solarillumination, heat localization simulates a phase change of the ionicliquid of RCA 100 from the solid state to the liquid state to facilitatethe capture of CO₂ gas in the RCA 100 due the fact that absorption ofCO₂ by an ionic liquid is greater in the liquid state of the ionicliquid than in the solid state of the ionic liquid.

As indicated in step S230 of FIG. 2, after sufficient CO₂ capture, RCA100 is removed from exposure to thermal energy source 110 (FIG. 1B).Thereafter, with reference to FIG. 1C and step S240 of FIG. 2, RCA 100is washed with a solution 120, e.g., an aqueous calcium hydroxide(Ca(OH)₂) solution, that serves to convert the captured CO₂ and removethe converted CO₂ from RCA 100 as filtrate from the wash. The filtrateincludes the byproducts 130 of the CO₂ capture and washing from RCA 100,as detailed below.

More specifically, with reference to FIG. 1C and step S240 of FIG. 2,the physical and chemical reactions involved in the washing of the CO₂captured RCA 100 with solution 120 are described and represented belowin equations (1), (2), (1)+(2), and (3). As will be appreciated in viewof the following, this enables the reuse of RCA 100 for multiple cyclesof CO₂ capture and conversion into useful byproducts 130, e.g., CaCO₃and H₂O.

Ca(OH)₂ (aq)+CO₂ (g)→CaCO₃ (s)+H₂O (l)  (1)

CaCO₃ (s)+CO₂ (g)+H₂O (l)

Ca(HCO₃)₂ (aq)  (2)

Ca(OH)₂ (aq)+2CO₂ (g)

Ca(HCO₃)₂ (aq)  (1)+(2)

Ca(HCO₃)₂ (aq)+Ca(OH)₂ (aq)

2CaCO₃ (s)+2H₂O (l)  (3)

Since ionic liquids strongly adsorb CO₂, successful washing of CO₂ fromthe ionic liquid of RCA 100 requires a solution 120 that binds CO₂ morestrongly than the ionic liquid of RCA 100. Once such solution 120 isaqueous Ca(OH)₂.

The reaction of Ca(OH)₂ with CO₂ to form calcium carbonate and calciumbicarbonate, provided in equations (1), (2), and (1)+(2) above, is wellknown. Ca(OH)₂ primarily produces CaCO₃, as indicated in equation (1)above, but forms Ca(HCO₃)₂ in the presence of excess CO₂, as indicatedin equation (2), above.

The use of a solution 120 having a low concentration of Ca(OH)₂ incombination with an excess of CO₂ selectively forms the solubleCa(HCO₃)₂ species that can be washed from RCA 100. The absorption of CO₂into a Ca(OH)₂ solution 120 is more efficient if the concentration ofCa(OH)₂ is low. Indeed, previous studies have shown that lowerconcentrations of Ca(OH)₂ lead to most of the CO₂ absorbed in thesolution to form a mixture of soluble ions, mainly bicarbonate. As such,a low concentration of Ca(OH)₂ in solution 120, e.g., a 0.01 M Ca(OH)₂solution, to wash the CO₂ from RCA 100 may thus be utilized.

RCA 100, having been washed as detailed above, may then be re-used tocapture additional CO₂, convert the captured CO₂, and wash the convertedCO₂ from RCA 100 as filtrate, similarly as detailed above andillustrated in FIGS. 1A-1C and steps S210-S240 of FIG. 2.

Referring to FIG. 1D and step S250 of FIG. 2, byproducts 130 obtainedfrom the filtrate resulting from the washing of the CO₂-captured RCA 100are separated. Separation of the filtrate into CaCO₃ and H₂O byproducts130 may be accomplished, for example, by allowing the filtrate to sitfor a suitable time, e.g., 5 days, until the excess CO₂ escapes from thefiltrate leaving the precipitated CaCO₃ and H₂O behind, or may befacilitated by treating the filtrate with additional aqueous Ca(OH)₂solution to precipitate out the calcium as CaCO₃, leaving CaCO₃ and H₂O.Via either method, or other suitable method, the result is an output ofCaCO₃ and H₂O, wherein the number of moles of H₂O formed is equal to thenumber of moles of CO₂ absorbed. As noted above, CaCO₃ has many usessuch as in water treatment and in the manufacture of many differentproducts across many different industries. The usefulness and importantof water needs no elaboration.

With general reference to FIGS. 1A-1D, RCA 100, as mentioned above,includes a material matrix holding an ionic liquid. Exemplary materialmatrices and ionic liquids forming RCA 100 are detailed below, althoughother suitable material matrices and ionic liquids forming RCA 100 arealso contemplated and within the scope of the present disclosure. Theionic liquid for RCA 100 is selected to have a melting point rangebetween 30° C. and 70° C. such that, when RCA 100 is exposed to solarthermal energy source 110, the thermal energy simulates a phase changein the ionic liquid from the solid state to the liquid state via heatlocalization, and such that the ionic liquid remains in the solid statein the absence of exposure to thermal energy source 110. Such aconfiguration is advantageous due the fact that absorption of CO₂ by anionic liquid is greater in the liquid state of the ionic liquid than inthe solid state of the ionic liquid, as noted above. Further, a meltingpoint range between 30° C. and 70° C. also facilitates solarillumination at 1 sun and integration of the ionic liquid into thematerial matrix to form RCA 100.

With respect to exemplary ionic liquids suitable for use in forming RCA100, it is noted that, while most CO₂ absorption studies with ionicliquids have been performed using ionic liquids with methylimidazolium-based cations coupled with a host of other anions, it hasbeen found that fluorinated anions are significantly better in CO₂absorption compared to other anions, with the CO₂ absorption capabilityincreasing with an increasing degree of fluorination. High molecularweight of the cation also increases CO₂ absorption. In addition, toavoid loss of the ionic liquid in the washing step (see FIG. 1C and stepS240 in FIG. 2) using the aqueous Ca(OH)₂ solution, the ionic liquidshould be largely immiscible in water. Miscibility of an ionic liquid inwater depends on the water-ion interaction strength and the size of theions (larger ions are less miscible). The magnitude of the localizedcharge in the connecting atom also plays a role in miscibility. Twoexemplary, commercially-available ionic liquids meeting theabove-detailed criteria are C10MI.BF₄ and C16MI.Tf₂N.

In addition to commercially available ionic liquids, fluorinated ionicliquids may also be utilized such as, for example, the fluorinatedimidazolium ionic liquid [CF₃(CF₂)₇(CH₂)₃MI][(CF₃—CF₂SO₂)₂N],abbreviated as FIL. This ionic liquid has a melting point of 56° C. andis a suitable ionic liquid for use in RCA 100 given that it will meltwithin the working temperatures detailed above and, being a long-chainfluorinated system, would produce good CO₂ absorption. While thisfluorinated ionic liquid is one example, other long-chain fluorinatedmethyl-imidazolium ionic liquids may also be utilized in RCA 100.

Continuing with general reference to FIGS. 1A-1D, the material matrix ofRCA 100 is selected to hold the ionic liquid and enable heatlocalization using a thermal energy source such as solar energy. Morespecifically, the material matrix is selected to include: (1) highabsorption in the solar spectrum, (2) low thermal conductivity forlocalizing thermal energy, (3) high permeability and porosity to hold alarge volume of the ionic liquid, (4) hydrophobicity to avoid theretention of water in the material matrix, and (5) oleophilicity toabsorb and retain the ionic liquid in the material matrix.Two-dimensional graphene, for example, meets the above-noted criteriaand, in particular, possesses high mechanical strength, low density,permeability and porosity, hydrophobicity and oleophilicity. Thus,graphene aerogels are suitable candidates for the material matrix of RCA100 to hold the ionic liquid of RCA 100.

One particular graphene aerogel and method of manufacturing the same isdetailed below, although other suitable graphene aerogels, othermaterial matrices, and/or methods of manufacturing are also contemplatedand within the scope of the present disclosure. First, 100 mg ofL-phenylalanine is dissolved in 5 mL of distilled water. Once dissolved,5 mL of graphene oxide is added to the solution, and the solution ispoured into a 25 mL vial for sonication for 10 minutes. Aftersonication, the vial is placed in a hot oil bath at 95° C. for 48 hoursto afford a wet hydrogel. The hydrogel is then freeze dried for 48 hoursat −65° C. to obtain the graphene aerogel.

With reference to FIG. 3, in conjunction with FIGS. 1A-1D, anexperimental system 300 for evaluating CO₂ capture, e.g., the amount ofCO₂ absorbed in RCA 100, with solar illumination is illustrated anddescribed below. System 300 includes a CO₂ cylinder 304 containing CO₂gas; an absorption chamber 330; a sample holder 335, e.g., an acrylicsample holder, disposed within the absorption chamber 330 and includingthe “SAMPLE,” i.e., RCA 100; a fiber glass window 340 enabling solarillumination from solar illuminator 350 to pass therethrough intoabsorption chamber 330; a gas output 380; a temperature sensor 370; apressure sensor 375, e.g., a pressure transducer; and a computer 390 fordata acquisition and analysis. Absorption chamber 330 includes an inputfor receiving CO₂ gas CO₂ cylinder 304 and an output for outputtingresultant gas to gas output 380.

In the experiments using system 300, the “SAMPLE” was positioned withinsample holder 335 within absorption chamber 330 and solar illuminator350 activated until the temperature within absorption chamber 330,measured via temperature sensor 370, e.g., a thermocouple, reached aconstant value above the melting point of the ionic liquid to be tested.The pressure in absorption chamber 330 was monitored using pressuresensor 375. Outputs of temperature sensor 370 and pressure sensor 375were connected to computer 390, and the generated data was collected bya suitable program, e.g., a LabView® program, available from NationalInstruments of Austin, Tex., USA. The pressure within absorption chamber330 was maintained between 2 bar and 6 bar and the temperature withinabsorption chamber 330 was maintained at 25° C. for approximately 40minutes during each experiment. The amount of CO₂ captured (in terms ofmole fraction) was calculated using the observed drop in pressure usingthe ideal gas equation.

Turning to FIG. 4, in conjunction with FIGS. 1A-1D, another experimentalsystem 400 for evaluating the amount of CO₂ absorbed in RCA 100 isillustrated and is described below. System 400 includes an N₂ cylinder402 containing N₂ gas, a CO₂ cylinder 404 containing CO₂ gas, mass flowcontrollers 403, 405 for the N₂ cylinder 402 and CO₂ cylinder 404,respectively, a gas mixer 410, a temperature controller 420, anabsorption chamber 430 including the “SAMPLE,” i.e., RCA 100, a fiberglass window 440 enabling solar illumination from solar illuminator 450to pass therethrough into absorption chamber 430, a gas output 460, atemperature sensor 470, an output gas analyzer 480, and a computer 490for data acquisition and analysis.

In the experiments, to evaluate the amount of CO₂ absorbed in RCA 100, aknown mass and mixture of N₂ and CO₂ gas was prepared from N₂ cylinder402 and CO₂ cylinder 404 utilizing mass flow controllers 403, 405, andgas mixer 410, and was passed into absorption chamber 430 (containingRCA 100) at a known pressure. The temperature of the mixture wascontrolled using temperature controller 420. Solar irradiation of 1kWm⁻² from solar illuminator 450 was applied to RCA 100 withinabsorption chamber 430, through fiber glass window 440, to simulatephase change of the ionic liquid in RCA 100. The output gas receivedfrom gas output 460 was then analyzed using gas analyzer 480 andcomputer 490. The temperature of the output gas was also monitored usingtemperature sensor 470 to evaluate phase change of the ionic liquid inRCA 100. Utilizing the above experimental system 400 and knowing theinitial mass flow of the gases and the difference between the initialpercentage of CO₂ and the final percentage of CO₂ after capture, theamount of CO₂ absorbed by RCA 100 was readily determined. Of course,other suitable experimental systems may also be utilized.

With reference to FIGS. 5A-5D, experimental results from differentexperiments of CO₂ capture in accordance with the materials and methodsof the present disclosure are illustrated for various ionic liquids asthe ionic liquid of RCA 100 (FIG. 1A) and two-dimensional graphene asthe material matrix of RCA 100 (FIG. 1A).

FIGS. 5A and 5B, more specifically, illustrate Fourier-TransformInfrared (FTIR) spectra for the capture of CO₂ using C10MI.BF₄ as theionic liquid (FIG. 5A), C16MI.Tf₂N as the ionic liquid (FIG. 5B), and afluorinated ionic liquid (FIL) as the ionic liquid (FIG. 5B).

As illustrated in FIGS. 5A and 5B, the FTIR spectra for the above-notedionic liquids after CO₂ absorption indicate a clear peak for CO₂ at 2400cm⁻¹, in accordance with earlier reports of CO₂ FTIR measurements. Toconfirm that the peaks were not due to atmospheric CO₂, IR measurementswere conducted after purging the compartment with nitrogen gas to removeatmospheric CO₂. The IR spectrum of pure water was also obtained, asillustrated in FIG. 5A. Multiple trials consistently revealed a CO₂ peakfor the ionic liquid samples only, verifying the capture of CO₂. Nochanges were observed in the base ionic liquid patterns, therebyindicating that the CO₂ was absorbed in the ionic liquids viaphysisorption. Experimental setups similar to the ones detailed above(see FIGS. 3 and 4) were also used to quantify CO₂ capture in the RCA100 (FIG. 1A) with the above-noted ionic liquids.

FIG. 5C illustrates the results of pressure drop experiments conductedto quantify the CO₂ capture of the above-noted ionic liquids in terms ofmole fraction. FIG. 5C, more specifically, shows the mole fraction ofcaptured CO₂ as a function of pressure. These experiments were conductedfor RCA 100 (FIG. 1A) containing above-noted ionic liquids (C16MI.Tf₂N,C10MI.BF₄, and FIL). Solar irradiation of one sun was incident on thesample to stimulate solid-liquid phase change. As shown, the capturedCO₂ in RCA 100 (FIG. 1A) using FIL as the ionic liquid is slightlyhigher than that using C16MI.Tf₂N as the ionic liquid, likely due to thehigher degree of fluorination in FIL.

FIG. 5D shows the percentage drop of CO₂ as a function of pressure forRCA 100 (FIG. 1A) with C16MI.Tf₂N as the ionic liquid, RCA 100 (FIG. 1A)with C10MI.BF₄ as the ionic liquid, and RCA 100 (FIG. 1A) with FIL asthe ionic liquid. As shown in FIG. 5D, the maximum drop in percentage ofCO₂ in the gas mixture is observed for the RCA 100 (FIG. 1A) with FIL asthe ionic liquid. This trend is consistent with the mole fraction ofcaptured CO₂ for these ionic liquids. Further, these results confirm theabsorption selectivity for CO₂ over N₂. Therefore, the selective captureof CO₂ in RCA 100 (FIG. 1A) is confirmed from these experiments.

FIG. 6A illustrates experimental results, in the form of FTIR spectra,of the CO₂ captured ionic liquid of RCA 100 (FIG. 1A) and the ionicliquid of RCA 100 (FIG. 1A) after washing with solution 120 (aqueous0.01M Ca(OH)₂ solution; FIG. 1C) to obtain precipitated CaCO₃, for eachof the above-noted ionic liquids. As illustrated, the disappearance ofthe CO₂ peak at −2400 cm⁻¹ after washing the ionic liquids with theCa(OH)₂ solution confirms the effectiveness of the washing process.

The absorption of CO₂ into a Ca(OH)₂ solution is more efficient if theconcentration of Ca(OH)₂ is low. This is because lower concentrations ofCa(OH)₂ lead to CO₂ absorbed in the solution, forming a mixture ofmainly soluble bicarbonate ions. 0.01 M Ca(OH)₂ solution was used towash the CO₂ out of RCA 100 (FIG. 1A) with FIL as the ionic liquid. FIL,being mostly immiscible in water, remains unchanged, while the CO₂ isconverted to the soluble HCO₃— species and is collected in the filtrate.Conversion of the CO₂ to soluble HCO₃ ⁻ is confirmed by its presence inthe filtrate via Ultraviolet-visible (UV-Vis) spectroscopy, as shown inFIG. 6B. Note that the UV-Vis spectrum was obtained soon after the RCA100 (FIG. 1A) was washed with the Ca(OH)₂ solution. From theseobservations, the presence of Ca(HCO₃)₂ in the filtrate can beconfirmed, implying effective washing of the RCA 100 (FIG. 1A) andconversion of the absorbed CO₂.

An electronic pH meter with a measuring probe (not shown) was used tocompare the pH levels between the calcium hydroxide solution before andafter washing the CO₂-impregnated RCA 100 (FIG. 1A), for each of theionic liquids noted above (C10MI.BF₄, C16MI.Tf₂N, and FIL) for threetrials to confirm the reproducibility of the results. A drop in pH wasobserved in the filtrate compared to the starting Ca(OH)₂ solution usedfor washing the ionic liquids, as shown in FIG. 6C. This experiment thusimplicates the consumption of OH⁻ to form the less basic HCO₃ ⁻ speciesin solution, responsible for the drop in pH. Soluble HCO₃ ⁻ is benign,but it is not the most commercially useful form of carbonate species. Aconversion to a more useful product is thus desirable. PrecipitatedCaCO₃ enjoys widespread use in a variety of industries, includingpaints, plastics, papers, and sealants. Therefore, to precipitate CaCO₃from Ca(HCO₃)₂ solution, the solution was left to stand. Once the excessCO₂ escapes from the solution, precipitated CaCO₃ is left behind, whichwas verified by the FTIR spectrum shown in FIG. 6D. The spectrum showspure CaCO₃ as compared to a reference spectrum of commercial CaCO₃.

FIG. 7 illustrates experimental results testing for repeatability over aplurality, e.g., five, cycles, wherein FIL is used as the ionic liquidof RCA 100 (FIG. 1A) and the final percentage composition of CO₂ ismeasured after each cycle. Although FIG. 7 illustrates the results fromrepeated CO₂ absorption and washing over multiple cycles using RCA 100(FIG. 1A) with FIL used as the ionic liquid, similar results would applyto the other ionic liquids detailed above. In these results, a nearlyconstant drop in the percentage of CO₂ was observed in the gas mixtureover multiple trials, thereby confirming the repeatability of RCA 100(FIG. 1A).

Continuing with reference to FIG. 7, more specifically, the gas analyzersetup and protocol detailed above was used to evaluate the reusabilityof RCA 100 (FIG. 1A) to yield the plot of percentage composition of CO₂in the resulting mixture as a function of repetition (at 4 bar operatingpressure). It was found that the percentage composition of the finalmixture remained constant for multiple cycles, thereby demonstrating thereusability of RCA 100 (FIG. 1A). FIG. 7 also shows the conductivity ofwater obtained from the reaction after the precipitation of CaCO₃.Similar conductivity is observed over five cycles as seen from the graphof FIG. 7.

FIGS. 8A and 8B illustrate the byproducts 130, including precipitatedCaCO₃ and water, in a test tube after the first cycle compared to afterthe fifth cycle, thus providing visual confirmation of the reusabilityof RCA 100 (FIG. 1A).

Materials, systems, and methods for capturing CO₂ and converting thecaptured CO₂ into useful byproducts in accordance with the presentdisclosure are detailed above, as is the verification of these materialsand methods through experimentation. Persons skilled in the art willunderstand that the features specifically described hereinabove andshown in the accompanying figures are non-limiting exemplaryembodiments, and that the description, disclosure, and figures should beconstrued merely as exemplary of particular embodiments. It is to beunderstood, therefore, that the present disclosure is not limited to theprecise embodiments described, and that various other changes andmodifications may be effected by one skilled in the art withoutdeparting from the scope or spirit of the disclosure.

What is claimed is:
 1. A method of capturing CO₂ and converting thecaptured CO₂ into useful byproducts, the method comprising: providing amaterial including a material matrix holding an ionic liquid; exposingthe material to a source of thermal energy to capture CO₂ within thematerial; removing the material from exposure to the source of thermalenergy; and washing the material with a solution to convert the capturedCO₂ and wash the converted, captured CO₂ from the material as filtrate.2. The method according to claim 1, further comprising separating thefiltrate into at least one useful byproduct.
 3. The method according toclaim 2, wherein separating the filtrate into at least one usefulbyproduct includes allowing the filtrate to sit for a period of time. 4.The method according to claim 2, wherein separating the filtrate into atleast one useful byproduct includes treating the filtrate withadditional solution.
 5. The method according to claim 2, wherein thefiltrate is separated into at least two useful byproducts and wherein atleast one of the useful byproducts is H₂O.
 6. The method according toclaim 2, wherein one of the at least one byproducts is CaCO₃.
 7. Themethod according to claim 2, wherein the filtrate is separated into atleast two useful byproducts including CaCO₃ and H₂O.
 8. The methodaccording to claim 1, wherein the solution is an aqueous Ca(OH)₂solution.
 9. The method according to claim 1, further comprisingrepeating, a plurality of additional times: exposing the material to thesource of thermal energy to capture CO₂ within the material; removingthe material from exposure to the source of thermal energy; and washingthe material with the solution to convert the captured CO₂ and wash theconverted, captured CO₂ from the material as filtrate.
 10. The methodaccording to claim 1, wherein exposing the material to the source ofthermal energy includes exposing the material to solar illumination. 11.A material configured to capture CO₂ and able to be washed of thecaptured CO₂, the material comprising: an ionic liquid having a meltingpoint of from 30° C. to 70° C., the ionic liquid configured to captureCO₂ in response to exposure to a thermal energy source; and a materialmatrix that is permeable, porous, hydrophobic, and oleophilic, thematerial matrix holding the ionic liquid therein.
 12. The materialaccording to claim 11, wherein the material matrix is an aerogel. 13.The material according to claim 11, wherein the material matrix includesa graphene aerogel.
 14. The material according to claim 11, wherein theionic liquid is a commercially-available ionic liquid or a fluorinatedionic liquid.
 15. The material according to claim 11, wherein the ionicliquid is one of:C10MI.BF₄;C16MI.Tf₂N; orCF₃(CF₂)₇(CH₂)₃MI][CF₃—CF₂SO₂)₂N.
 16. The material according to claim11, wherein the ionic liquid is washable to wash out CO₂ capturedtherein.
 17. A system configured to capture CO₂ and convert the capturedCO₂ into useful byproducts, the system comprising: a CO₂ absorber,including: an ionic liquid having a melting point of from 30° C. to 70°C., the ionic liquid configured to capture CO₂ in response to exposureto a thermal energy source; and a material matrix that is permeable,porous, hydrophobic, and oleophilic, the material matrix holding theionic liquid therein; and a washing solution, the washing solutionconfigured to wash captured CO₂ from the CO₂ absorber.
 18. The systemaccording to claim 17, wherein the material matrix includes a grapheneaerogel.
 19. The system according to claim 17, wherein the ionic liquidis fluorinated.
 20. The system according to claim 17, wherein thesolution is an aqueous Ca(OH)₂ solution.